Further Analyses of the Climax Cloud-Seeding Experiments

Abstract

A further examination of the Climax I and II randomized cloud-seeding experiments has revealed the following. 1) Cloud seeding had no effect on precipitation in Climax I after the control stations had been chosen halfway through the experiment. 2) Faulty execution of the randomization scheme resulted in a misleading precipitation climatology and a misleading relationship between cloud-top and 500-mb temperatures for the control days. 3) The method of assigning upper-level winds and temperatures to experimental days emphasized widespread, synoptic-scale weather systems with cloud tops far above 500 mb rather than the orographic ?blanket? clouds that were sought. 4) Particle trajectory calculations show that it is unlikely that the silver iodide released from the ground could have affected precipitation at Climax in southwest flow, the category for which the greatest seeding effect was reported.